Question: $\sum\limits_{y=1}^{2 }{{(1-y)}}=$
Explanation: What is the question asking for? $\sum$ tells us to find the sum. The question is asking for the sum of the values of $1-y$ from $y = 1$ to $y = 2$. Evaluating $\begin{aligned} \sum\limits_{y=1}^{2 }{({1-y})}&= (1-1) + (1-2) \\\\ &= 0 + (-1) \\\\ &= -1\end{aligned}$ The answer $\sum\limits_{y=1}^{2 }{({1-y})}=-1$